ES2307703T3 - POSITION MEASUREMENT DEVICE FOR THE DETERMINATION OF THE ABSOLUTE POSITION. - Google Patents

Abstract

The position measuring device has a scanning unit (AE) for scanning a sequential pseudo-random code (C) having a series of code elements (C1,C2,C3) extending in the measuring direction (X), each having 2 complementary partial regions. The binary information (B1,B2,B3) for each code element is obtained by comparing scanned signals for both partial regions. An Independent claim for an absolute position measuring method is also included.

Description

Position measuring device for Determination of the absolute position.

The present invention relates to a position measuring device for determining the absolute position according to the preamble of claim one.

For the determination of the position of two moving objects with each other known measuring devices of the incremental positions that detect relative movements of objects with each other at measurement stages or certain increments. The incremental position measurement devices used for this they include, as a rule, a scale with a track with a incremental measurement graduation, which is linked to one of the two objects as well as an exploration unit that is linked to the Another of the two objects. Through an optical scan, Magnetic, inductive or capacitive are generated in a known way periodic incremental signals dependent on displacement.

For the rest, the so-called absolute position measuring devices, which comprise the side of the scale a track with a sequential code of several bit words, set, for example, as a code pseudorandom, from whose exploration the position can be determined absolute along the respective measurement section. The respective sequential code along the direction of measurement is composed of a correspondingly selected sequence of signals logic or bits that adopt, for example, the values ZERO (0) and ONE (one). To increase detection security in such systems, also knows how to derive each individual logic signal or each bit of a word of bits from a predetermined sequence of two partial zones with different optical characteristics. In this way corresponds, for example, the logic signal ZERO (0) to the sequence of a translucent and a non-translucent partial zone, by on the contrary, the logical signal ONE (1) corresponds to the sequence of a non-translucent partial zone and a translucent zone on the track. An encoding of this type is called Manchester coding; for this refers, for example, to Figure 1 in the publication "Absolute position measurement using optical detection of code patterns ", J. T. M. Stevenson, J. R. Jordan, J. Phys. E: Sci. Instrum. 21 (1988), p. 1140-1145.

With the use of such Manchester encodings in absolute position measurement devices occur two typical problem complexes. First of all it must be guaranteed basically that the partial zones are read correctly or that the detector elements used for this are selected so correct to assign to a given sequence of two zones partial also the correct logic signal or bit value correct ZERO (0) or ONE (1). With reference to this problem, the publication mentioned above does not provide data additional. Otherwise, absolute position information generated by a Manchester encoding is not enough accurate regarding the resolution. This means that it is expected as a rule combine absolute position information with a position information of an incremental position measurement of higher resolution. To generate from the information of absolute code of more general resolution an information of higher resolution position, which can be combined with the measurement of the incremental position, in the code word recently explored is first determined by interpolation with edge transitions between different partial zones and, by therefore, a general position within the respective word of code, with which the incremental information is then combined. Such a procedure is also proposed, for example, in the publication mentioned above. Is considered problematic that the precision resulting from an interpolation with edge of this type is negatively influenced by the effects of diffraction and due to the possibly present divergence of the source of light, so that errors can occur during position determination. This is particularly the case when  higher position measurement devices are used resolution with smaller widths of partial areas.

From EP 0 635 700 A1 it is known a device for measuring the generic position in which generates absolute position information from the Scan of a single encoded track. One of the examples of embodiment describes a coded track with three partial zones different.

A position measuring device for the determination of the absolute position is additionally known as from GB 2 297 840 A. For this it is used in parallel to a track coded pseudorandomly a track additional with three different partial zones.

US 4,774,494 describes a variant additional graduation with three different partial zones, where they have different colors. The graduation proposal, however, is used in a measuring device the incremental position.

It is the objective of the present invention to indicate a position measuring device that is suitable for the determination of the absolute position and with which, from a single track, you can get a signal of the absolute position readable with a higher resolution.

This goal is solved by a device of position measurement with the characterizing properties of the claim 1.

       \ newpage
    

Advantageous embodiments of the position measuring device according to the invention from the measures indicated in the claims dependent of claim 1.

According to the invention, it is now foreseen use on the side of the scale in total at least three zones partials with different optical properties in a track. For this, in a first combination of two successive partial zones, different, a first logical signal is clearly assigned and a second combination of two successive, different partial zones, a second logical signal is clearly assigned. The first and the Second combination differ from each other.

By means of these measures it is guaranteed from here on forward a clear coding of the bit word position recently read without the need for this information additional. To this is added that in this way you can also ensure detection of possible read signals so wrong.

Due to the periodic arrangement of one of the partial areas on the scale can be guaranteed by corresponding measurements on the exploration side that in addition to absolute position information can also be generated by minus a general incremental signal, which can be used to the formation of an absolute high position value resolution. In this case an interpolation with edge, as explained above, that is, based on the considerations according to the invention can now also be perform high position measurement devices resolution.

Basically you can arrange each of the three different partial zones periodically on the scale, that is to say, both the first, the second and the third zones partial.

Regarding the configuration of the third parties partial areas there are different possibilities, when first and second partial zones have optical properties complementary. Thus, for example, in a possible variant for the third partial zones you can select a property optic that is between the optical properties of the first and second partial zones configured in a complementary way. In an additional variant, the third partial zones present a periodic substructure from which you can obtain a additional precise incremental signal that serves to increase additional resolution during position determination absolute.

On the exploration side it is required, for the generation of the different scanning signals due to the measures according to the invention, in a possible embodiment only a single detector equipment with several elements of detector through which all the signals of exploration.

The present invention can be used, obviously, systems in light and in systems for incident light; they can also be configured according to the invention linear and rotary position measuring devices. By otherwise, considerations according to the invention are also can transfer to systems that comprise on the side of the scale more than three different partial zones.

Additional advantages and details of the present invention from the following description of Examples of realization by the attached drawings.

It shows:

In Figure 1, a schematic view of a first embodiment of the measuring device of the position according to the invention with a first variant of a adequate scale along with an exploration unit;

In Figure 2, an elevation view on a part of a second example of realization of a suitable scale together with a detector equipment indicated schematically;

In Figure 3a, a first modular scheme for the explanation of the processing of the signals generated by the detector equipment in Figure 2;

In Figure 3b, a second modular scheme for the explanation of the processing of the signals generated by the detector equipment in Figure 2;

In Figure 4, an elevation view on a part of a third example of realization of a suitable scale together with a detector equipment indicated schematically;

In Figure 5, a modular scheme for the explanation of the processing of the signals generated by the equipment  of detector of Figure 4;

In Figures 6a - 6c, respectively signals generated from the area of the scale shown in Figure Four.

In Figure 1 it is represented schematized a first embodiment of a device position measurement according to the invention including a First example of realization of a suitable scale. He position measuring device, configured as a system with linear light, it includes a scale 1, whose configuration concrete will be explained in more detail throughout the following description, and a mobile scanning unit 20 at least in one direction of measurement x with respect to scale 1. On the side of the scanning unit 20 is arranged a light source 21, a collimator optics 23 as well as detector equipment 22, which it consists of a plurality k of individual detector elements 22.1, 22.2., .... 22.k, which are arranged periodically in the direction of measurement x. As a light source 21 it is considered in this point, for example, an LED, as detector equipment 22 serves a series of photodiodes with adjacent detector elements 22.1, ... 22.k.

Scale 1 and scan unit 20 of position measuring device are linked with two objects mobile to each other in the direction of measurement x, whose position relative has to be determined. The two objects can be, by example, a tool and a piece to work on a machine numerically controlled tool. With the help of the device position measurement according to the invention can be generated  by a photoelectric exploration of scale 1 and the combination after the different scan signals generated, a POS_ {ABS} high position absolute position information. As scan signals a position signal is produced Absolute ABS, a general incremental signal INC_ {G} as well as a precise incremental signal INC_ {F}, which will be explained in detail below. The combination of the different scan signals to form position information Absolute POS_ {ABS} can be done both directly in the position measuring device according to the invention as in a subsequent evaluation unit, not represented, to the that the different scan signals are supplied. A evaluation unit of this type can be, by way of example, a numerical control of machine tools.

For further description of an example of concrete realization of a suitable scale reference is made now to Figure 2, which shows an elevation view on a part of a scale 10 together with a detector equipment 2 indicated of Schematic form, suitable for exploration. How can observe from Figure 2, scale 10 presents first, second and third partial zones TB1, TB2, TB3 arranged at along the direction of measurement x, which they possess in the sense of measurement x all the same width b_ {TB}, however, different optical properties In the present example of a scale 10 for a light system, the first partial zones TB1 opaque, the second partial zones TB2 are configured, completely translucent. For the rest, according to the invention a third category of partial zones TB3 is envisaged in The side of the scale. The third partial zones TB3 have a optical property in turn different from the first and the second partial zones TB1, TB2. In the embodiment example in Figure 2, the third partial zones TB3 are configured semi-translucent and therefore have an optical property that stands, with respect to the optical transmission characteristic, between the transmission characteristics of the first and the second partial zones TB1 and TB2. They have properties optics complementary to each other due to the configuration that You mentioned opaque or completely translucent.

In the example in Figure 2, the first zones partial TB1 are arranged along the direction of measurement x periodically on scale 10. Its period is indicated in successive as general graduation period TP_ {G} and it preferably corresponds to twice the width b TB of the partial zones TB1, TB2, TB3, that is,

100

The scale 10 represented comprises in principle a so-called Manchester coding. This essentially means  than to two different combinations of two partial zones TB3, TB1 or TB2, TB1 different, successive, is assigned respectively of Clearly a logical signal. In the present example it is assigned to a first combination of third and first partial zones TB3, TB1 successive the first logical signal ONE (1), to a second combination  of second and first successive partial zones TB2, TB1, the second logic signal ZERO (0). By the section represented in the Figure 2 of scale 10 is produced, therefore, starting from the left as a succession of the different logical signals, such as indicated, the sequence of bits or the word of bit 1; one; 0; 0; etc.  By such a sequence of several logical signals ZERO (0) and ONE (1) can be characterized along scale 10 in the measurement direction x in an known way an absolute position clear as a code word or a signal can be generated ABS absolute position. As an example, a sequence of this type of several logical signals can correspond to a pseudorandom coding, from which it can be derived an absolute position defined along the measurement scale 10.

The case of the light system that has been explained, the different optical properties of the different partial zones TB1, TB2, TB3 are optical translucences different; the first and second partial zones TB1, TB2 they have complementary optical properties for this, which in their time has as a consequence the configuration of the first zones partial TB1 completely opaque or the second partial zones TB2 completely translucent. Alternatively to the configuration explained of the system to light, obviously the configuration of partial zones TB1, TB2 also in reverse to the variant explained as partially opaque partial zones or fully translucent partial areas.

Otherwise it is possible to apply the principles according to the invention even in an incident light system. This would result in the different properties optical would then be different optical reflection properties of the partial zones TB1, TB2. As an example, then the first partial zones TB1 would be configured not reflective, on the contrary, the second partial areas TB2 reflective, or vice versa. Correspondingly, the property optics of the third partial zones TB3 would have to select in such a way that they present a reflection characteristic that will be placed between those of the first and second partial zones TB1, TB2, that is, by way of example, were configured semi-reflective

       \ global \ parskip0.930000 \ baselineskip
    

For the rest, within the framework of this invention there are additional possibilities for the realization of the different optical properties of the three partial zones TB1 - TB3 In this way, they could also have, for example, different colors. It would also be possible to configure them with periodic graduation substructures to present respectively different graduation rates, etc.

In addition, alternatively it is also possible assign the logic signals ZERO (0) and ONE (1) to other combinations  of the sequence of two successive partial zones of those explained In the previous example.

For the exploration of scale 10, provides on the side of the scanning unit a team of detector 2, comprising a series of detector elements 2.1 - 2.12 periodically arranged in the direction of measurement x. In the present example, detector equipment 2 comprises in total twelve detector elements 2.1 - 2.12 that have in the sense of the measurement respectively a width b_ {DET} = b_ {TB} / 2, which  corresponds to half the width b_ {TB} of the zones partial TB1 - TB3 on scale 10.

During the exploration of scale 10, produce for the different partial zones TB1 - TB3 on the side of detector elements 22.1 - 22.6 signal values or levels defined signal, where for subsequent explanation are assigned to the individual partial zones TB1 - TB3 the following levels Signal on the detector side:

TB1:

Signal Level 0

TB2:

Signal Level 1

TB3:

0.5 signal level

In the example shown in Figure 2, as consequently, the detector elements 2.1, 2.2 provide the signal level 0.5, detector elements 2.3, 2.4, the level of signal 0, detector elements 2.9, 2.10, signal level 1, etc. To the default combinations of two signal levels successive in the sense of measurement x of partial zones different certain ZERO logic signals (0) are now assigned, ONE 1). For this, the following rules of assignment:

101

In this example, by switching technique, the allocation rules are transformed in such a way that you always generates the difference of the signal levels of partial zones Adjacent TB1 - TB3 and the resulting difference signal DIF will be Assign according to the following guidelines clearly to one of the two logic signals ZERO (0) or ONE (1):

102

If a DIF difference signal occurs that is deviates from the two ranges of values that have been indicated, it is say, by way of example, DIF <0, this is interpreted as a error during the selection of the correct detector elements 2.1 - 2.12. Thus, for example, reading a first and third partial zone TB1, successive TB3 supplies a signal of difference with the DIF value = -0.5, analogously to this, first and second partial zones TB1, TB2 successive supply a difference signal with the value DIF = -1. In both cases, due to the measures according to the invention basically by the single formation of the DIF difference signal without another Additional information can be verified if the elements of the detector have been selected correctly.

Obviously, within the framework of this invention can be used, as an alternative to standards and allocation guidelines explained, also standards alternatives.

Due to the periodic arrangement on the side of the scale of the first partial zones TB1 with the period of general graduation TP_ {G} is possible, in addition to generating POS absolute position signals generate in the manner that has been explained, in addition to this, even a general incremental signal periodic INC_ {G}. The general incremental signal INC_ {G} has a signal period SP_ {G} that is obtained in a known manner at from the general graduation period TP_ {G} of the first partial zones TB1 on scale 10. The incremental signal General generated in this way INC_ {G} can be combined after known way with the absolute position signal POS to form an absolute position value POS_ {ABS} of higher resolution. For the generation of the general incremental signal INC_ {G} is not requires no additional detector equipment, for this you can use even detector equipment 2 that has been explained above with detector elements 2.1 - 2.12 periodically arranged in the sense of measurement, which commute afterwards correspondingly and they provide in the output side the general incremental signal INC_ {G}.

A possible switching variant for detector elements 2.1 - 2.12 of the example of Figure 2 are schematically depicted in Figures 3A and 3B. Both Figures 3A and 3B respectively show the required switching for generating the general incremental signal INC_ {G} so such as switching for position signal generation Absolute ABS The representation of the switching variants is performed in separate figures only for reasons of simplicity

With reference 3.1 - 3.4 they are indicated in the Figure 3A respectively addition elements that sum up the detector element scanning signals 2.1 - 2.12 equiphasic to sum signals S1 - S4; with the reference 4.1, 4.2, elements of difference formation are indicated which, a from the four addition signals S1 - S4, they generate known the two general incremental signals INC_ {G, 0} or, INC_ {G, 90} with phase shift between them of 90º.

For the generation of the position signal Absolute ABS is first provided in accordance with Figure 3B supply the scanning signals of the detector elements 2.1 - 2.3 to an addition element 3.5 and scan signals of detector elements 2.2, 2.4 to an addition element 3.6, which supply the sum signals S5, S6 on the output side. For the rest, by the difference formation elements D1, D2 the generation of difference signals DIF1, DIF2 is performed at from the scanning signals of the detector elements 2.1, 2.3 as well as 2.2, 2.4. The addition and difference signals S5, S6, D1, D2 are then supplied to four elements of evaluation K1 - K4, which are configured, for example, as comparators with default comparator thresholds and those that perform the indicated assignments. For signal generation of the absolute ABS position only the evaluation of the difference signals formed DIF1, DIF2 according to the guidelines that have been explained above. Through both evaluation elements K3, K4 is therefore performed checking of whether the respective difference signal DIF1, DIF2 is located in the value range 0.75 <DIF1, DIF2 or the range of values 0.75> DIF1, DIF2 and the corresponding assignment or output of the logical signal ONE (1) or ZERO (0) as absolute position sub-signal ABS ', ABS' '. Since in the present example by partial zone TB1 - TB3 two detector elements are arranged respectively, generate two absolute sub-signals ABS ', ABS' 'that continue processing in the case of the correct reading as a signal Absolute position ABS.

To check if the detector elements are have been selected correctly provided in the present example otherwise the generation of one or two error signals F ', F' '. For this, the addition signals S5, S6 are evaluated in both evaluation elements K1, K2 according to the conditions indicated and the output signals supplied by the elements of evaluation K1, K2 are supplied below with the ABS ', ABS' 'absolute position subwords of the elements of evaluation K3, K4 to the elements of association 5.1, 5.2. After of the XOR association that takes place in that place occur in the output side error signals F ', F' ', which may be adopted by values of 0 or 1. The value F '= 1 or F' '= 1 is interpreted in this case as the correct selection of the detector elements, the value F '= 0 or F' '= 0 as the wrong selection of the elements of detector.

An additional embodiment example of a scale configured properly including scanning provided for it is explained below by the Figures 4, 5 and 6a - 6c. Figure 4 shows in a similar way the figure described above an elevation view on a part of a scale 10 'together with a detector equipment 22' indicated schematically, which can be used in a linear backlight position measuring device. At side of the scale are arranged in turn according to the invention three partial zones TB1 ', TB2', TB3 'with different properties optical along the direction of measurement x. The first and second partial zones TB1 ', TB2' are configured as in the example explained above in a completely opaque way or completely translucent.

It is different from the previous example of realization, on the one hand, the configuration of the third partial zones TB3 ' and, on the other hand, the fact that now the third partial zones TB3 'are arranged along the measuring scale 10' so periodic in the sense of measurement x. The third zones partial TB3 'comprise in this example a periodic sub-graduation which is composed in turn of first and second sub-zones TB_ {SUB1}, TB_ {SUB2} periodically arranged in the direction of the x measurement with different optical properties. The first and second sub-zones TB_ {SUB1}, TB_ {SUB2} are configured in the example shown opaque or completely translucent; the period of disposition of first and second sub-zones TB_ {SUB1}, TB_ {SUB2} is hereinafter referred to as the precise graduation TP_ {F} and indicates in the direction of measurement x the extension of the first and second sub-zones partial TB_ {SUB1}, TB_ {SUB2} successive. Besides the generation of an absolute ABS position signal and a signal incremental general INC_ {G} analogously to the previous example, this variant of a suitable 10 'scale allows due to the selection of the configuration of the third partial zones TB3 ' also the creation of a precise incremental signal INC_ {F}, whose resolution is greater than that of the general incremental signal INC_ {G}. The formation of the absolute position value POS_ {ABS} therefore, it is possible with even greater precision.

       \ global \ parskip1.000000 \ baselineskip
    

In the case of this example it occurs together with certain dimensioning measurements on the scanning side that they have to explain then, otherwise, a so-called single field exploration during the generation of the different incremental signals INC_ {G}, INC_ {F}. This is why you have to understand an exploration in which all the components of the phase shift signal of incremental signals INC_ {G} or INC_ {F} are produced by scanning a single Graduation period TP_ {G} or TP_ {F} on the 10 'scale. Be have to consider a decisive advantage of an exploration of this type its insensitivity with respect to local contamination of the scale, since then all the partial signals generated with phase shift, which contribute to the different signals incremental INC_ {G}, INC_ {F}, are influenced by it mode.

Basically you have to keep the following relationship (2) for the general graduation period relationship TP_ {G} and the precise graduation period TP_ {F} on the side of 10 'scale:

103

with n = 1, 2, 3, ...

In addition to generating a position signal Absolute ABS, the scale, along with certain measures on the side of exploration, which will be explained below, allows as already mentioned the generation of a general incremental signal INC_ {G} as well as a precise incremental signal INC_ {F}. By simplicity, hereafter always refer to a signal incremental general or accurate INC_ {G} or INC_ {F}, even though in practice, a couple of signals of this type that have a phase shift with each other of 90º.

The general incremental signal INC_ {G} is produced as the previous example from the exploration of TB3 'partial zones arranged periodically with the period of general graduation TP_ {G} on the 10 'scale, where in this case the third partial zones TB3 'are now arranged correspondingly periodic. The precise incremental signal INC_ {F} is generated by scanning the substructure of graduation in the third partial zones TB3 ', where there is a periodic provision of partial sub-zones with the precise graduation period TP_ {F}.

In addition to the absolute ABS position signal, in this variant, therefore, two signals are available incremental INC_ {G}, INC_ {F} with different resolution for the additional processing and the formation of an absolute value of POS_ {ABS} position with high resolution. In the case of the example of a general graduation period TP_ {G} = 160 \ mum selected on the side of the 10 'scale and a precise graduation period TP_ {F} = 20 \ mum occur with a scan corresponding general incremental signals INC_ {G} with the signal period SP_ {G} = 160 µm or incremental signals you need INC_ {F} with the signal period SP_ {F} = 20 µm. In this example, as a consequence, the magnitude n is selected at from Eq. (2) n = 4.

For the generation of the different signals of ABS scan, INC_ {F} and INC_ {G} are required on the side of the scanning unit, particularly along with the configuration or the dimensioning of detector equipment 22 ', certain measures in the position measuring device according to the invention, which will be explained below.

As can be seen from Figure 4, the detector equipment 22 'used comprises in this example globally k = 64 individual detector elements 22.1 '- 22.64' which are periodically arranged in the direction of the measurement x.

To guarantee exploration in this example Single-field mentioned above are arranged on the side of the detection by general graduation period TP_ {G} globally N = 16 detector elements. In the general case of an exploration desired single field, during which, by graduation period scanned, four incremental signals have to be generated with 90º phase shift, they have to be arranged according with the following relationship

104

with n = 2, 3, ...

detector elements per graduation period general TP_ {G} on the scanning side, when the ratio of General and accurate graduation period has been selected from according to Eq. (2). A dimensioning of this type guarantees the single field scan during signal generation precise incremental INC_ {F} and during the generation of general incremental signals INC_ {G}.

Basically, to ensure the exploration of single field during the planned generation of four signals from phase shift scan from a single period graduation, they must be arranged as a result at least Four detector elements per graduation period. This means that in the case of the single generation of a signal incremental general INC_ {G} according to the previous example, as a consequence at least four elements have to be arranged of detector by general graduation period TP_ {G} or a integer multiple of this. In the case of the generation additional of an accurate incremental signal INC_ {F} has to guarantee analogously to this that by graduation period precise TP_ {F} at least four detector elements are arranged in the sense of measurement or, in a given case, a multiple of whole number of this.

Figure 5 illustrates the switching of the detector elements 22.1 '- 22.64' inside the equipment detector 22 of the example of Figure 4, which are provided for the generation of the different ABS scan signals, INC_ {G}, and INC_ {F}. For this, for reasons of simplicity only represents a part of the k = 64 detector elements 22.1 '- 22.64 'used in total for signal generation.

As already mentioned above, in the practice occurs respectively a pair of incremental signals General with phase shift INC_ {G, 0}, INC_ {G, 90}, and precise incremental signals INC_ {F, 0}, INC_ {F, 90}, which, so far for simplicity they have been named respectively general incremental signals INC_ {G} or incremental signals precise INC_ {F}.

With references 23.1 - 23.17 are indicated in the switching scheme of Figure 5 respectively elements of addition that make a sum of the present signals respectively on the input side. For the elements of difference formation indicated with references 24.1 - 24.5 se perform a subtraction or difference formation of the signals present at the entrance. With the help of the elements indicated by references 25.1 - 25.5 or 26.1 - 26.2 the respective arithmetic operation indicated with the input signals present.

For the generation of the different signals of ABS scan, INC_ {G} and INC_ {F} are required here example at least 16 detector elements and the corresponding switching them, by way of example, the elements of detector 22.1 '- 22.16'. The second to fourth blocks planned otherwise in the example with respectively 16 elements of additional detector 22.17 '- 22.32', 22.33 '- 22.48' and 22.49 '- 22.64 'basically provide during the scan identical scan information and only improve the resulting signal intensity during scanning. That is to say, Each sixteenth detector element supplies the information of equiphasic exploration

Next, the generation of the ABS absolute position signal in the present example. The generation  of the two logic signals ZERO (0) and ONE (1) are based again on certain allocation rules. To the different partial zones TB1 '- TB3' in turn certain signal levels of agree with

TB1 ':

Signal Level 0

TB2 ':

Signal Level 1

TB3 ':

0.5 signal level

In turn, to certain combinations predetermined two successive signal levels in the sense of the measurement x is assigned logic signals ZERO (0), ONE (1), where In this example the following allocation rules apply:

105

To decide on this variant on a scale if the detector elements have been selected correctly, in addition to the formation of a DIF difference signal from signals from adjacent partial areas is additionally performed the formation of an addition signal SUM from the signals of adjacent partial zones. The difference and addition signals resulting are assigned according to the following guidelines of assignment to the two logic signals ZERO (0) and ONE (1).

106

In the example of first and third partial zones TB1 ', TB3' successive the difference signal is produced
DIF = -0.5 and the addition signal SUM = +0.5. In accordance with the previous guidelines, the ZERO logic signal is assigned to both signals, that is, the selection of the detector elements is carried out correctly. In the case of third and first partial zones TB3 ', TB1' successive, on the contrary, it would be produced as a difference signal
DIF = +0.5 and as an addition signal SUM = +0.5; in accordance with the previous guidelines for the assignment of addition and difference signals, this would mean for the difference signal DIF the assignment of the logical signal ONE (1) and for the addition signal SUM the assignment of the logic signal ZERO (0 ). From this discrepancy a selection, in a given case, not correct of the detector elements can then be deduced. As in the previous example, as a consequence it is possible to determine from the scan of the scale whether the detector elements have been selected correctly or not.

For the transformation by technique of switching, in this example the scan signals are added resulting from the first eight detector elements 22.1 '- 22.8 'by the addition element 23.1 to signal S1, the scanning signals of the second eight detector elements 22.9 '- 22.16' by the second addition element 23.2 until the S2 signal. From the summed signals S1, S2 is formed to continuation with the help of the difference formation element 24.1 the DIF difference signal; with the help of the addition element 23.17, the sum signal SUM. SUM addition signal and signal difference are then supplied to an association element 27, performing an XOR association of the DIF and SUM signals of according to the allocation guidelines that have been explained previously. In the output of the association element 27 is then the absolute ABS position signal that can be followed processing or the corresponding bit values or signals logical.

For the generation of the incremental signal general INC_ {G} or the pair of general incremental signals with phase shift INC_ {G, 0}, INC_ {G, 90} a switching of the detector elements in the manner represented in Figure 5. At this point, in relation to the switching variant selected it is mentioned that the selection of the elements of detector that have to be switched is performed in a known way depending on the general graduation period TP_ {G} on the scale.

Similarly, in the context of the generation of the precise incremental signal INC_ {G} or the signal pair precise incrementals with INC_ {F, 0} phase shift, INC_ {F, 90} refers to the switching of the elements detector as shown in Figure 4. Also in this case the selection of the detector elements that have to be commute is based on the precise graduation period TP_ {F} on  the scale.

The ABS scan signals, INC_ {G} e INC_ {F} that occur from such a switching of detector elements 22.1 - 22.64 or signal pairs corresponding INC_ {F, 0} and INC_ {F, 90}, ABS, INC_ {G, 0} e INC_ {F} are represented in Figures 5a-5c.

Within the framework of the present invention obviously the most diverse modifications can be conceived with  regarding the variants that have been explained so far.

In this way it is possible, for example, to modify the second embodiment explained to such an extent that in the side of the scanning unit is arranged in front of the equipment of detector a scanning grid that is configured, by example, as phase grid. Through an exploration grid this type can be generated due to the resulting interaction with the precise graduation period on the scale in the plane of detection in a known way a so-called Vernier interference. In turn, from this Vernier interference you can obtain an incremental signal with a defined signal period.

Otherwise it is mentioned that evidently you can also vary the detector equipment, particularly the number of the detector elements used in the framework of the previous considerations.

Therefore, in addition to the examples described, in the context of the present invention there are other alternatives of realization.

Claims (18)

1. A position measuring device composed of a scale (1; 10; 10 ') as well as a unit of mobile scan (20) in a measuring direction (x) with respect to the scale (1; 10; 10 ') which, from the exploration of the scale (1; 10; 10 '), determines the absolute position of the unit of exploration (20) with respect to the scale (1; 10; 10 '), where the scale consists of a track that extends at least in a measurement direction and on the track alternately arranged zones partials of equal width with different optical properties and in the track are arranged at least first, second and third zones partials (TB1, TB2, TB3; TB1 '; TB2'; TB3 ') with different optical properties, characterized because the scanning unit assigns to a first combination of two successive different partial zones (TB1, TB3, TB1 ', TB3') clearly a first logical signal (1) and assigns to a second combination of two successive different partial zones (TB2, TB3, TB2 ', TB3') clearly a second logical signal (0), where the first and the second combination differ between yes. 2. The position measuring device according to claim 1, characterized in that one of the partial zones (TB3; TB3 ') is provided with a general graduation period (TP_G) on the scale (10) of periodic form in the sense of measurement (x). 3. The position measuring device according to claim 2, characterized in that the general graduation period (TP_G) corresponds to twice the width (b_ {TB}) of the partial zones (TB1, TB2 , TB3, TB1 ', TB2', TB3 ') with different optical properties. 4. The position measuring device according to claim 1, characterized in that the first and second partial zones (TB1, TB2, TB1 ', TB2') have complementary optical properties to each other. 5. The position measuring device according to claim 1, characterized in that the first logical signal (1) is assigned to the first and third successive partial zones (TB1, TB3, TB1 ', TB3') and the second and successive third partial zones (TB2, TB3, TB2 ', TB3') the second logical signal (0) is assigned. The position measuring device according to claim 1, characterized in that a sequence of several logical signals (0, 1) characterizes a clear absolute position along the direction of measurement (x). 7. The position measuring device according to claim 4, characterized in that the third partial zones (TB3) have an optical property that is situated between the properties of the two complementary properties of the first and second partial zones (TB1, TB2). The position measuring device according to claim 7, characterized in that the third partial zones (TB3) are semi-translucent configured. 9. The position measuring device according to claim 4, characterized in that the third partial zones (TB3) comprise a periodic sub-graduation with a precise graduation period (TP_ {F}), which is composed of sub- Partial areas arranged periodically (TB_ {SUB1}, TB_ {SUB2}) with different optical properties. 10. The position measuring device according to claim 9, characterized in that the partial sub-zones (TB_ {SUB1}, TB_ {SUB2}) have complementary optical properties to each other. 11. The position measuring device according to claims 3 and 9, characterized in that the precise graduation period (TP_) is selected according to the relationship 107 with n = 1, 2, 3, ... 12. The position measuring device according to claim 4 or 10, characterized in that the complementary optical properties of each other are selected as follows:

-

opaque / completely translucent or

-

reflective / nonreflective.

         \ newpage
      

13. The position measuring device according to claim 1, characterized in that the scanning unit (20) comprises at least one light source (21) as well as a detector equipment (2; 22; 22 ') for the scan of the scale (1; 10; 10 '), where the detector equipment (2; 22; 22') serves both for the generation of an absolute position signal (ABS) and a general incremental signal (INC_ { G}). 14. The position measuring device according to claim 1, characterized in that the detector equipment (2; 22; 22 ') comprises a periodic arrangement in the direction of measurement (x) of individual detector elements (22.1 - 22.k; 2.1 - 2.6; 22.1 '- 22.64'). 15. The position measuring device according to claims 13 and 14, characterized in that at least four detector elements (2.1) are arranged in the direction of measurement (x) per general graduation period (TP_ {G}). - 2.12). 16. The position measuring device according to claim 13, characterized in that the detector equipment (22 ') additionally serves to generate a precise incremental signal (INC_ {F}). 17. The position measuring device according to claims 14 and 16, characterized in that at least four individual detector elements (22.1 '- 22.64') are arranged in the direction of measurement (x) by precise graduation period. . 18. The position measuring device according to claim 13, characterized in that an scanning grid is arranged in front of the detector unit.